Peripheral nervous system involvement frequently occurs in systemic lupus erythematosus (SLE) patients. However, chronic inflammatory demyelinating polyneuropathy (CIDP) is an unusual presentation that can develop before, after, or simultaneously with the onset of SLE. This paper reports the case of a 20-year-old man with diabetes mellitus (DM) and CIDP accompanied by SLE. The patient complained of progressive weakness in the bilateral upper and lower extremities that had begun 2 months prior to this visit. He was diagnosed with CIDP and treated with intravenous immunoglobulin (IVIG), but had little improvement. A plasma exchange was then scheduled, but it was not helpful either. The patient developed polyarthritis, oral ulcer, and a worsening of his muscle weakness two weeks later. A neurologic examination revealed 3/5 muscle strength in the upper and lower extremities, absent deep tendon reflex (DTR), and impaired position sense. The patient was diagnosed with SLE because of pancytopenia, lymphopenia, pleuropericardial effusion, proteinuria, high titer anti-nuclear antibody (ANA), and anti-dsDNA. A kidney biopsy revealed stage IV lupus nephritis. The patient received 3 pulses of methyl prednisolone, 6 months of cyclophosphamide, and a high daily dose of prednisolone. His proteinuria improved, and he regained the ability to ambulate with a normal gait after about 2.5 months. To the best of the authors’ knowledge, the concurrency of CIDP with SLE and DM has not been previously reported.